<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <title> id  </title>
        <style>
            #test
            {
                color: aqua;
                background-color: brown;
            }
            .test1
            {
                color: aqua;
                background-color: brown;
                font-size: 100px;
            }
        </style>
    </head>
    <body>
        <h1 id="test"> 蓝字红底 </h1>
        <span class="test1">变大</span>
    </body>
</html>